(1) Field of the Invention
This invention relates to a new bi-layer attenuating phase shifting material and method of forming the new bi-layer attenuating phase shifting material using two layers of AlSixOy wherein x may be different in each layer and y may be different in each layer. The new bi-layer material is particularly useful in 193 nanometer lithography.
(2) Description of the Related Art
Phase shifting materials and attenuating phase shifting materials are of considerable importance in the formation of phase shifting photomasks.
U.S. Pat. No. 6,150,058 to Tu et al. describes methods of making attenuating phase shifting masks using different exposure doses.
U.S. Pat. No. 6,087,047 to Mitsui et al. describes a half-tone phase shift mask blank.
U.S. Pat. No. 5,480,747 to Vasudev describes attenuated phase shifting masks with buried absorbers.
U.S. Pat. No. 6,261,725 B1 to Tzu et al. describes a method for modulating the phase angle of a phase shift mask used in deep ultra violet photolithography. The phase angle of the phase shift layer may be incrementally changed by chemical treatment.
U.S. Pat. No. 5,714,285 to Tu et al. describes the use of a composite of (LaNiO3)x(TiO2)1-x to form attenuating phase shifting blanks and masks.
U.S. Pat. No. 5,667,919 to Tu et al. describes an attenuated phase shifting mask blank, an attenuated phase shifting mask blank, and methods used to form them. The attenuating phase shifting material is TaxSiyO1−x−y tantalum-silicon oxide.
A paper entitled “Attenuated phase shift mask materials for 248 and 193 nm lithography”, by B. W. Smith et al., J. Vac. Sci. Technol., B, Vol. 14(6), pages 3719-3723, November/December 1996 describes materials which may be used as attenuated phase shift mask films.